1. Field of the Invention
This invention relates to a system for detecting failure of a fuel pressure sensor, particularly to a system for, in an internal combustion engine employing natural gas as fuel, discriminating failure of fuel supply line pressure detecting means or fuel pressure sensor from fluctuation in air intake pipe pressure.
2. Description of the Related Art
An internal combustion engine powered by compressed natural gas was recently proposed in Japanese Laid-open Patent Application No. 7(1995)-217,485. In this type of engine, methane or other natural gas stored in a fuel tank (gas cylinder) under high pressure (250 kg/cm.sup.2) is supplied to fuel injection valves through a fuel supply passage (line).
A pressure regulator inserted in the fuel supply line regulates the pressure of the high-pressure natural gas to around 2 kg/cm.sup.2, more exactly so as to maintain the pressure differential between the supplied fuel pressure and the air intake pipe pressure at a constant value. A pressure sensor is provided to detect the fuel supply line pressure downstream of the pressure regulator.
Since desired fuel injection control cannot be conducted when this pressure sensor experiences a broken electrical connector, a shift in output characteristic or other such abnormality (failure), rapid and accurate detection of pressure sensor abnormality (failure) is desirable.